How placebo modulates orthodontic pain remains largely unknown. The present study aimed to investigate the placebo modulation of brain activity associated with orthodontic pain using fMRI.

How placebo modulates orthodontic pain remains largely unknown. The present study aimed to investigate the placebo modulation of brain activity associated with orthodontic pain using fMRI. 23 voluneers were recruited in a longitudinal fMRI experiment. At both the baseline and the one-month follow-up, orthodontic separators were placed between right lower molars 24 hours before MRI scans. At baseline, the subjects were scanned without placebo while all subjects took placebos half an hour before the scan at follow-up. Scans include a bite/non-bite task fMRI and a followed resting state fMRI. A generalized linear model was used to identify pain-regulating network from task fMRI, and functional connectivity analysis of pain related brain regions was performed to study the possible modulation of placebo on connectivity of pain-regulating networks using resting-state fMRI.

Inclusion Criteria:

• Female, 20-25 years old;
• Right handed;
• Understand the Visual Analog Scale;
• No history of serious illness, surgery, psychiatric disorders or neurological;
• No history of drug or alcohol abuse;
• No Maxillofacial diseases, agomphiasis, caries, metal filling material or crown;
• Individual normal occlusion with no orthodontic treatment history.

Exclusion Criteria:

• claustrophobic or experienced obvious adverse reactions including fear, nausea, vomiting
• discomfort during the scan process or during menstruation.